1. Field of the Invention
The present invention concerns a silver halide photographic emulsion. Particularly, it relates to a silver halide photographic emulsion high in silver iodide content and having improved sensitivity and improved shelf stability as well as improved sensitivity to short time exposure, by controlled chemical sensitization. It further relates to a thermally developable photosensitive material using an emulsion with high silver iodide content, which has improved properties due to a novel chemical sensitization method.
2. Description of the Related Art
In recent years, a demand for improvements of sensitivity, shelf stability, development progress characteristics, gradation, graininess and sharpness of siliver halide photographic photosensitive material has been increased more and more. Silver halide emulsions are usually subjected to chemical sensitization by using various kinds of chemical substances in order to obtain desired sensitivity and gradation. Specifically, the method of chemical sensitization include chalcogen sensitization such as sulfur sensitization, selenium sensitization and tellurium sensitization, noble metal sensitization using noble metals such as gold and reduction sensitization by using a reducing agent or a reductive atmosphere. Each of these methods may be used alone or in combination with others. While various chemical sensitization methods have been reported for silver iodo bromide emulsions in which the silver iodide content is as low as 40% or less and the silver chloride emulsions, there are few concrete knowledge so far of effective chemical sensitization methods for photographic emulsions high in silver iodide content with the silver iodide content in a range from 80% to 100%.
In Journal of Photographic Science, vol. 8, p 118, issued in 1960, it was reported that sensitization of silver iodide grains by sulfur sensitization was difficult. Subsequently, it was reported in Journal of Photographic Science, vol. 22, p 228, issued in 1974 or vol. 28, p 163, issued in 1980 that the silver iodide emulsion was sensitized by sulfur sensitization at pAg of 7.5. It was also reported that sensitization was conducted by epitaxial formation in U.S. Pat. Nos. 4,459,353 and 4,142,900. However, it was difficult in the photographic emulsions high in silver halide content to improve the properties such as sensitivity or development performance to a practically useful level even by using the means described above.
In recent years, dry photographic processing has been demanded keenly in the medical field or in the field of print making with a view point of environmental preservation and space saving. In the fields described above, digitalization has been developed. Systems has widely spread in the field, in which an image information is inputted into computers, stored and then processed, if necessary, outputted on a photosensitive material by a laser image setter or a laser imager, at a place where the image is required, through communication device, and converted to a real image by development at the same place. The photosensitive material is required to be capable of recording with high-illumination laser exposure and required to give a sharp black image high in resolution and definition. As the digital imaging recording materials, various types of hard copy systems utilizing pigments and dyes such as ink jet printers and electrophotography have been used as general image forming systems. However, they are unsatisfactory in point of the image quality (sharpness, graininess, gradation and tone), which decides the diagnostic performance as in medical images, and the recording speed (sensitivity). Hence, they have not reached a level capable of replacing existent wet process silver salt films for medical use.
On the other hand, thermal image forming systems utilizing organic silver salts are described, for example, in the specifications of U.S. Pat. Nos. 3,152,904 and 3,457,075, and xe2x80x9cThermally Processed Silver Systemsxe2x80x9d by B. Shely (Imaging Processes and materials, Neblette, 8th edition, edited by Sturge, V. Walworth, and A. Shepp, page 2, 1996). Particularly, thermally developable photosensitive materials generally have a photosensitive layer in which a photosensitive silver halide, a reducing agent, a silver salt capable of reduction (for example, organic silver salt) and optionally, a toning agent for controlling the tone of silver dispersed in a matrix of a binder.
The thermally developable photosensitive material is heated to a high temperature (for example, 80xc2x0 C. or higher) after imagewise exposure. Then a black silver image is formed on the thermally developable photosensitive material by oxidation/reduction reaction between a reducible silver halide or a reducible silver salt, which function as oxidizers, and a reducing agent. The oxidation/reduction reaction is promoted by a catalytic effect of latent images of a silver halide formed by the exposure. As a result, a black silver image is formed in an exposed region. The thermally developable photosensitive materials are disclosed in many literatures including U.S. Pat. No. 2,910,377 and JP-B No. 43-4924. Further, Fuji Medical Dry Imager-FM-DPL has been marketed practically as an image forming system for medical use.
Since the image forming systems utilizing the organic silver salt described above have no fixing step, the shelf stability of the image after the development, particularly worsening of a printout when exposed to light, cause a significant problem. As a method of improving the printout, a method of utilizing silver iodide formed by conversion of an organic silver salt was disclosed in U.S. Pat. No. 6,143,488 and EP 0922995. However, only insufficient sensitivity could be obtained by the method of converting the organic silver salt with iodine as disclosed therein, and it was difficult to set up an actual system. In addition, sensitive materials utilizing silver halide are described in WO97-48014, WO48015, U.S. Pat. No. 6,165,705, JP-A No. 8-297345 and JP No. 2785129. However, only insufficient levels of sensitivity and fogging could be attained and none of them could endure the practical use as the sensitive material for laser exposure.
The purpose of the present invention is to provide a photographic emulsion high in silver iodide content, which has high sensitivity and excellent shelf stability. The second purpose of the invention is to provide a thermally developable photosensitive material having high sensitivity and low Dmin and high Dmax, and also excellent in shelf stability of image to the light after development.
The foregoing purposes of the present invention can be attained by the following silver halide photographic emulsion and the thermally developable photosensitive material according to the present invention described below.
A silver halide photographic emulsion containing silver iodide in an amount of 80% by mol to 100% by mol and chemically sensitized by at least one of a chalcogen sensitization method and a gold sensitization method at pAg of 1.5 to 7.0 range.
A thermally developable photosensitive material containing at least one kind of a photosensitive silver halide, non-photosensitive organic silver salt, a reducing agent and a binder on one surface of a support in which the photosensitive silver halide contains silver iodide in an amount of 80% by mol to 100% by mol and chemically sensitized by at least one of a chalcogen sensitization method and a gold sensitization method at pAg of 1.5 to 7.0 range.
The thermally developable photosensitive material as described above in which the photosensitive silver halide contains silver iodide in an amount of 90% by mol to 100% by mol.
The thermally developable photosensitive material as described above in which the grain size of the photosensitive silver halide is from 10 nm to 45 nm.
The thermally developable photosensitive material as described above in which the photosensitive silver halide is contained by 1 mol to 7 mol based on 1 mol of the non-photosensitive organic silver salt.
The thermally developable photosensitive material as described above, wherein the grains are formed under a condition in which the organic silver salt is not present and the photosensitive silver halide emulsion is chemically sensitized.
The high silver iodide photographic emulsion as described above, chemically synthesized by at least one of the chalcogen sensitization method and the gold sensitization method under the condition in which pAg is 6.5 or less, preferably, 6.0 or less, further preferably, 5.5 or less and is 1.5 or more, preferably, 2.0 or more and, further preferably, 2.5 or more.
The silver halide photographic emulsion as described above in which the chalcogen sensitization is selected from tellurium sensitization, selenium sensitization and sulfur sensitization, preferably from tellurium sensitization and selenium sensitization and, further preferably, is tellurium sensitization.
The silver halide photographic emulsion as described above in which the gold sensitization is gold/chalcogen sensitization, which is a combination of gold sensitization and chalcogen sensitization, wherein the gold/chalcogen sensitization is selected from the group consisting of gold/sulfur sensitization, gold/selenium sensitization, gold/tellurium sensitization, gold/sulfur/selenium sensitization, gold/sulfur/tellurium sensitization, gold/selenium/tellurium sensitization, and gold/sulfur/tellurium sensitization.
The silver halide photographic emulsion as described above further subjected to reduction sensitization in addition to the chalcogen sensitization and gold sensitization.
The silver halide photographic emulsion as described above in which the photosensitive silver halide grains have an epitaxially formed portion, which portion preferably contains silver bromide and silver chloride.
The silver halide photographic emulsion as described above in which the photosensitive silver halide grains contain dislocation lines or lattice defects.
The silver halide photographic emulsion as described above in which the grain size of the photosensitive silver halide grains is 0.5 xcexcm or less, preferably, 0.1 xcexcm or less and, further preferably, 0.05 xcexcm or less, and is 0.005 xcexcm or more, and the coefficient of variation of the grain size is 30% or less, preferably, 25% or less and, particularly preferably, 20% or less.
The silver halide photographic emulsion as described above in which the photosensitive silver halide grains contain group VIII metals, for example, Fe, Ir, Ru, Rh and Os, and organic or inorganic four- to six-coordinate complexes thereof.
The silver halide photographic emulsion as described above in which the photosensitive silver halide emulsion contains a sensitizing dye, preferably, a cyanine dye or a merocyanine dye.
The silver halide photographic emulsion as described above in which the photosensitive silver halide emulsion contains compounds described in U.S. Pat. Nos. 5,413,905, 5,482,825, 5,747,235, 5,747,236, 5,994,051, and 6,054,260.
The thermally developable photosensitive material as described above in which the photosensitive silver halide emulsion is the silver halide photographic emulsion as described above.
The silver halide photographic emulsion and the thermally developable photosensitive material as described above which are exposed by a laser beam.
The thermally developable photosensitive material as described above in which the peak wavelength of the laser beam is in a range from 600 nm to 900 nm.
The thermally developable photosensitive material as described above in which the peak wavelength of the laser beam is in a range from 300 nm to 500 nm.
According to a first feature, the invention provides a silver halide photographic emulsion (A) containing silver iodide in an amount of 80% by mol to 100% by mol and chemically sensitized by at least one of methods of a chalcogen sensitization method, or a gold sensitization method under the condition in which pAg is in a range from 1.5 to 7.0.
According to a second feature, the invention provides a silver halide photographic emulsion, wherein the photosensitive silver halide contains silver iodide in an amount of 90% by mol to 100% by mol and chemically sensitized by at least one of methods of a chalcogen sensitization method, or a gold sensitization method under the condition in which pAg is in a range from 1.5 to 7.0.
According to a third feature, the invention provides a silver halide photographic emulsion, wherein a grain size of the silver halide in the silver halide photographic emulsion (A) is in a range from 5 nm to 70 nm.
According to a fourth feature, the invention provides a silver halide photographic emulsion, wherein the grains of the photosensitive silver halide in the silver halide photographic emulsion (A) are formed under the condition that a non-photosensitive organic silver salt is not present and chemically sensitized.
According to a fifth feature, the invention provides a silver halide photographic emulsion, wherein the silver halide photographic emulsion (A) is chemically sensitized by at least one of methods of chalcogen sensitizing method and gold sensitizing method under the condition in which pAg is in a range from 1.5 to 6.5.
According to a sixth feature, the invention provides a silver halide photographic emulsion, wherein the chalcogen sensitization applied to the silver halide photographic emulsion (A) is selected from tellurium sensitization, selenium sensitization and sulfur sensitization.
According to a seventh feature, the invention provides a silver halide photographic emulsion, wherein the gold sensitization applied to the silver halide photographic emulsion (A) is gold chalcogen sensitization, which is a combination of gold chalcogen sensitization and chalcogen sensitization, including gold/sulfur sensitization, gold/tellurium sensitization, gold/sulfur/selenium sensitization, gold/sulfur/tellurium sensitization, gold/selenium/tellurium sensitization, and gold/sulfur/tellurium sensitization.
According to a eighth feature, the invention provides a silver halide photographic emulsion, wherein reduction sensitization is further applied in silver halide photographic emulsion (A) in addition to the chalcogen sensitization or gold sensitization.
According to a ninth feature, the invention provides a silver halide photographic emulsion, wherein the silver halide photographic emulsion (A) is exposed by a laser beam.
According to a 10th feature, the invention provides a thermally developable photosensitive material (B) having, disposed on it, at least one image forming layer containing at least one kind of a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder on one surface of a support, wherein the photosensitive silver halide contains 80% by mol to 100% by mol based on silver iodide, and chemically sensitized by at least one of methods of a chalcogen sensitization method and a gold sensitization method under the condition in which pAg is in a range from 1.5 to 7.0.
According to a 11th feature, the invention provides a thermally developable photosensitive material having, disposed on it, at least one image forming layer containing at least one kind of a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder on one surface of a support, wherein the photosensitive silver halide contains 90% by mol to 100% by mol based on silver iodide, and chemically sensitized by at least one of methods of a chalcogen sensitization method and a gold sensitization method under the condition in which pAg is in a range from 1.5 to 7.0.
According to a 12th feature, the invention provides a thermally developable photosensitive material, wherein the grain size of the silver halide in the thermally developable photosensitive material (B) is in a range from 5 nm to 70 nm.
According to a 13th feature, the invention provides a thermally developable photosensitive material, wherein the coating amount of the photosensitive silver halide grains in the thermally developable photosensitive material (B) is in a range from 0.5% by mol to 15% by mol based on 1 mol of a non-photosensitive organic silver salt.
According to a 14th feature the invention provides a thermally developable photosensitive material, wherein the grains of the photosensitive silver halide in the thermally developable photosensitive material (B) are formed under the condition that the non-photosensitive organic silver salt is not present, and chemically sensitized.
According to a 15th feature, the invention provides a thermally developable photosensitive material, wherein the thermally developable photosensitive material (B) is chemically sensitized by at least one of methods selected from chalcogen sensitizing method and gold sensitizing method under the condition in which pAg is in a range from 1.5 to 6.5.
According to a 16th feature, the invention provides a thermally developable photosensitive material, wherein the chalcogen sensitization applied to the thermally developable photosensitive material (B) is selected from tellurium sensitization, selenium sensitization and sulfur sensitization.
According to a 17th feature, the invention provides a thermally developable photosensitive material, wherein the gold sensitization applied to the thermally developable photosensitive material (B) is gold chalcogen sensitization, which is a combination of gold sensitization and chalcogen sensitization, including gold/sulfur sensitization, gold/tellurium sensitization, gold/sulfur/selenium sensitization, gold/sulfur/tellurium sensitization, gold/selenium/tellurium sensitization, gold/sulfur/tellurium sensitization.
According to a 18th feature, the invention provides a thermally developable photosensitive material, wherein reduction sensitization is further applied to the thermally developable photosensitive material (B) in addition to the chalcogen sensitization and the gold sensitization.
According to a 19th feature, the invention provides a thermally developable photosensitive material, wherein the thermally developable photosensitive material (B) is exposed by a laser beam.